/*
 * @lc app=leetcode.cn id=304 lang=java
 *
 * [304] 二维区域和检索 - 矩阵不可变
 */

// @lc code=start
class NumMatrix {
    int[][] sum;
    public NumMatrix(int[][] matrix) {
        int m=matrix.length;
        int n=matrix[0].length;
        sum=new int[m+1][n+1];
        for(int i=1;i<=m;i++){
            for(int j=1;j<=n;j++){
                sum[i][j]=sum[i-1][j]+sum[i][j-1]-sum[i-1][j-1]+matrix[i-1][j-1];
            }
        }
    }
    
    public int sumRegion(int row1, int col1, int row2, int col2) {
        return sum[row2+1][col2+1]-sum[row2+1][col1]-sum[row1][col2+1]+sum[row1][col1];
    }
}

/**
 * Your NumMatrix object will be instantiated and called as such:
 * NumMatrix obj = new NumMatrix(matrix);
 * int param_1 = obj.sumRegion(row1,col1,row2,col2);
 */
// @lc code=end

